Indicating device



Aug. 9, 1932. A. M. CURTIS INDICATING DEVICE Filed Oct. 18, 1950 v kv mv N .M W W 11% mv mw .b RT .Il 0R L. 1 Mw v E o 1 MM .um m mm s. Q m mw 1 ,s l 1 v @n mw mw VKL .Q k` s Nm. Nm.. m a. E S v n Patented Aug. 19, 1932 UNITED STATES lPATENT OFFICE AUSTEN M. CURTIS, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 0F NEW YORK TNDICATING VDEVICE Application led October 18, 1930. Serial No. 489,497.

This invention relates to indicating devices and more particularly to a device for indicating current variations in a plurality of circuits.

One form of instrument now employed for this purpose comprises a number of fine wires or conducting strings suspended in a magnetic field, each wire forming a part of the circuit, the current variations of which are to be studied and each wire being adapted to vibrate in accordance with variations in vthe current passing therethrough. These wires in vibrating intercept a beam of light and the shadows thus produced fall upon a moving light-sensitive film thereby producing a record of the motion of the Wires. The present practice is to mount these wires in the same plane and in order to prevent adjacent wires from contacting with each other they areV spaced apart from each other by a distance greater than the maximum amplitude of vibration of each wire. Such an arrangement, however, requires a relatively wide film and furthermore, due to diffusion, the shadows cast by the outside wires are more or less indistinct.

An object, therefore, of the present invention is to provide a device which permits the use of a relatively narrow film.

A further object is to provide such a device whereby the records produced on the lm are of uniform intensity.

In accordance with the present invention these and other objects are attained by mounting adjacent wires in different planes, all of which, however, are perpendicular to the axis of the magnetic field. In this arrangement adjacent wires may be placed close together without danger of contacting during vibration. Furthermore, the records produced are uniform since when he wires are grouped in close relationship the shadows produced are of uniform intensity.

A clearer understanding'of this invention may be had by reference to theaccompanying drawing in which Fig. 1 is a cross-sectional view of an oscillograph element embodying the features of this invention; Fig. 2 a plan view taken along line 2 2 of Fig. 1 ;v Fig.v 3 a detailed view showing the relative position of the strings with respect to each other; and Fig. 4 a detailed view showing the manner in which the strings are mounted.

.As shown by the drawing, this element consists of two sections, one section comprising a- U-shaped frame 10 upon which is mounted a housing 11 carrying condensing lenses 12 and 13, and a magnetic iron core 14 upon which is wound a field winding 15. A triangular shaped metallic pole piece 16 is secured to the face of the core 10 in such a manner that the cone shaped passage therethrough is in alignment with a similarly shaped passage in core 14. L The second section of the element consists of a metallic plate 17 which fits over the ends of the U-shaped frame 10, and is adapted to be securely clamped thereto as by spring clamps or by screws. A second triangular shaped pole piece 18 also provided with 'a cone shaped opening is secured to plate 17 in such a manner that the small opening 19 in its face is slightly separated from and directly opposite I a similar opening in the face of pole piece 16. A focusing lens 20 with its mounting 21 is threaded into a bracket 22 which is attached to plate 17, thus permitting adjustment of the lens.

r Three small wires 23, 24 and 25 which', for example, may be made from duralumin, are stretched between the small holes in the faces of pole pieces 16 and 18. These4 wires are stretched over ivory frets 57 and 58, the frets preferably being slotted'so that the wires are mounted in different planes, thus permitting them to vibrate in parallel planes without coming into contact with each other during vibration. A satisfactory alternative arrangement is to have the frets slotted so that alternate wires may vibrate without coming into contact with each other, One end of wiref23 is fastened to a tapered pin26 which is rotatably mounted in a brass supporting end piece 27 fastened to plate 17 by screws 28 the L-shaped member, screw 34 being used for obtaining the correct tension in the wire and screw 35 in combination with spring 36 being used lfor maintaining this tension. In like manner wires 24 and 25 are stretched over the ivory frets and the tension adjusted. Each wire is then made a. part ofa circuit through which the current to be studied is flowing. For example, when making wire 25 a part of a circuit the incoming lead is secured to a spring clip terminal 37 and the outgoing lead is connected to a similar terminal, which terminals are mounted on the U-shaped member 10 by means of screws and insulating strips 39 and 40. There is thus completed a circuit from the incoming conductor through spring clip 37, through terminal 42 which terminal as Well as the remaining terminals 40, 41, 43, 44 and 45 are secured to plate 17 by means of screws 46, 47 and 48 and insulating strips 49 and 50. From terminal 42 the circuit is completed through conductor 51, terminal 52, wirev 25, L-shaped member 53, stud 54, conductor back to the outgoing terminal. In like manner the remaining wires 23 and 24 are connected in different circuits which are to be studied.

In operation, the wires, 23, 24 and 25 are connected respectively into the circuits to be studied and the winding 15 excited, thereby setting up a magnetic field between the faces of the pole pieces 16 and 18.' rI`he light from lamp 56 passes through the condensing lenses 12 and 13, through the small openings in the pole pieces, through the focusing lens 2O where the light is properly focused by simply adjusting the position of the lens and then by any suitable arrangement onto a moving light-sensitive film 59. Inasmuch as the wires are mounted in a steady magnetic field any v'change in the strength of the current flowing therethroughwill cause them to vibrateaccordingly and since these wires are in the light path they will cast shadows, which shadows will be suitably reproduced on the light-sensitive film, thereby recording the changes which occur in the various circuits. Since these Wires are mounted in different planes they are permitted to vibrate Ifreely without interferingr with each other,

' thus permitting the various records to be suy perimposed on one another.

The resulting picture, when developed, shows a clear wave trace; against an opaque background and prints made from it show a black wave trace on a white background. Inasmuch as the records are superimposed upon one another,

a much narrower film may be used than heretofore possible.

While this invention has been described in connectionwith a three-wire oscillograph element, yet it is to be understood that equally favorable results may be obtained when using either a greater or less number of strings.

' What is claimed is:

1. 'An oscillograph comprising a plurality of vibrating members mounted parallel in dierent planes in the same magnetic field and adapted to vibrate in accordance with variations in electric current flowing therethrough, and means for recording the successive positions of each of said members.

2. An oscillograph comprising means for producing a steady magnetic eld, a plurality of members mounted parallel in different planes in said field and adapted to vibrate in response to variations in electric current flowing therethrough and means for casting shadows that may overlap Without mechanical interference between the wires in adjacent planes onto a light-sensitive film.

3. An oscillograph comprising means for producing a steady magnetic field, a plurality of members mounted parallel in said field and ada-pted'to vibrate in response to variations in electric current flowing through said members, means for producing superimposed'recprds of the vibrations of each of said memers.

4. An oscillograph comprising means for producing a steady magnetic field, aplurality of members adapted to vibrate in response to variations in electric current fiowing therethrough, a beam of light for casting shadows each indicating the instantaneous position of one of the members the members being mounted in said field in such a manner that adjacent members vibrate in different parallel planes and may traverse a major portion of the width of the beam to produce overlapping records, and means for recording the vibration of said members.

5. An oscillograph comprising a plurality of wires for vibration in a steady magnetic field under the influence of variable currents flowing therethrough with means for recording their vibrations on a single strip or ready for comparison of the relative vibrations of the wires, said means vincluding a lens system the Wires being adapted to vibrate in closely adjacent planes substantially in the focal plane of the lens system and perpendicular to the lines of'magnetic force in a manner such that the record of the motion of any wire may overlap that of an adjacent wire or wires for permitting a greater degree of variation or greater amplitude of vibration in each wire to permit more precise recording and better comparison of the currents flowing in the l 

